How is The Flash's police detective Eddie Thawne related to Eobard Thawne, AKA the Reverse-Flash? While The Flash doesn't beat out Superman or Wonder Woman, he still remains one of DC's most popular superheroes. The character debuted way back in 1940, with college student Jay Garrick accidentally inhaling some vapors following an experiment that grants him super speed.
Since then, many other characters have taken up The Flash mantle, with the most popular being Wally West and Barry Allen. Allen is arguably the most popular alter ego, with John Wesley Shipp playing the character in the cult live-action series from the early 1990s. Grant Gustin would later assume the role for The CW's Flash series that debuted in 2014. Ezra Miller also played Barry Allen in both Batman V Superman: Dawn Of Justice and Justice League, though it's unknown if he will return for a future DCEU project.
The Flash season 1 did a great job bringing the speedy superhero to life on the small screen, diving deep in the rich lore of the comic, whilst Gustin did a great job bringing Allen to life. The show also features a great supporting cast, including Tom Cavanagh (Scrubs) as Barry's mentor Harrison Wells and Rick Cosnett as Detective Eddie Thawne. The big twist of the first season is that Wells is actually supervillain Reverse-Flash, a metahuman from the future who is the literal opposite of The Flash in every respect. Eobard is also responsible for the death of Nora Allen when he traveled back in time and tried to kill Barry as a boy.
The other major reveal is the Reverse-Flash is actually Eobard Thawne, and Eddie is his distant ancestor. The show never provides an exact family tree to work out their relation to one another, but it appears Eobard is essentially the great-great-grandson of Eddie. In the original timeline of The Flash, Eddie would have married and had children, leaving a relatively uneventful life. This apparently marked him as something of a failure within the Thawne family, which featured many prominent scientists and politicians.
Eddie eventually proves to be Eobald's undoing, however, and shoots himself at the end of The Flash season 1. This has the effect of erasing the Reverse-Flash from the timeline since Eddie didn't have children. Eddie's noble, Looper-style sacrifice is one reason he's well remembered by fans of the show, but naturally, Eobald is eventually able to return via a convoluted series of events to cause Barry and his friends even more grief.